Field of the Invention
The present invention relates to a carbon dioxide recovery apparatus and a carbon dioxide recovery method.
Related Art
Recently, carbon dioxide recovery-storage technologies have received attention as effective countermeasures against global warming issues on fears of a global mass scale for recovering carbon dioxide. In particular, methods to recover carbon dioxide utilizing aqueous solutions have been studied as targeting thermal power stations and process exhaust gas.
Such a carbon dioxide recovery apparatus has been disclosed in Japanese Patent Application Laid-open 2009-214089, for example. The carbon dioxide recovery apparatus includes an absorbing tower which generates a rich liquid by absorbing carbon-dioxide-containing gas into an absorbing liquid, a releasing tower which generates a lean liquid by heating the rich liquid discharged from the absorbing tower to release and separate carbon dioxide along with steam and which returns the lean liquid to the absorbing tower, a first heat exchanger through which the lean liquid to be supplied from the releasing tower to the absorbing tower passes, a second heat exchanger through which carbon-dioxide-containing steam separated at the releasing tower passes, and a splitting device which splits the rich liquid discharged from the absorbing tower to the first and second heat exchangers. Here, the rich liquids introduced to the first and second heat exchangers are supplied to the releasing tower after performing heat exchange respectively with the lean liquid and the carbon-dioxide-containing steam.
With the above carbon dioxide recovery apparatus in the related art, heat energy included in the carbon-dioxide-containing steam which is separated at the releasing tower can be recovered at the second heat exchanger utilizing the split rich liquid. However, temperature of the rich liquid passing through the first heat exchanger is apt to be increased owing to decrease of flow quantity thereof. As a result, since temperature difference against the lean liquid being high temperature side fluid becomes small, there arises a problem that heat energy recovery quantity from the lean liquid at the portion is decreased compared to a case without splitting. The tendency becomes more apparent in a case that performance of the first heat exchanger is enhanced as taking measures such as increasing of heat-transfer area to reduce steam consumption of the carbon dioxide recovery apparatus.